U.S. patent number 6,210,420 [Application Number 09/233,298] was granted by the patent office on 2001-04-03 for apparatus and method for efficient blood sampling with lancet.
This patent grant is currently assigned to Agilent Technologies, Inc.. Invention is credited to J. Fleming Dias, Ganapati R Mauze.
United States Patent |
6,210,420 |
Mauze , et al. |
April 3, 2001 |
Apparatus and method for efficient blood sampling with lancet
Abstract
A technique for efficiently sampling blood from body tissue by
reducing pressure on the body tissue. In the present technique a
body tissue is placed under reduced pressure to improve perfusion
of blood in the body tissue before lancing. An embodiment of this
apparatus includes a lancet carried by a piston slidable in a
housing, a mechanism for transmitting mechanical energy internally
in the apparatus for creating the reduced pressure on the body
tissue. The apparatus also includes a driver that drives the lancet
for lancing. The apparatus has a head in the housing for contacting
the body tissue in an air-tight manner against suction forces. In
the head facing the body tissue is a channel in which the air
pressure can be reduced.
Inventors: |
Mauze; Ganapati R (Sunnyvale,
CA), Dias; J. Fleming (Menlo Park, CA) |
Assignee: |
Agilent Technologies, Inc.
(Palo Alto, CA)
|
Family
ID: |
22876696 |
Appl.
No.: |
09/233,298 |
Filed: |
January 19, 1999 |
Current U.S.
Class: |
606/182;
606/181 |
Current CPC
Class: |
A61B
5/15186 (20130101); A61B 5/150022 (20130101); A61B
5/150068 (20130101); A61B 5/150099 (20130101); A61B
5/150183 (20130101); A61B 5/150213 (20130101); A61B
5/150229 (20130101); A61B 5/150412 (20130101); A61B
5/150519 (20130101); A61B 5/15113 (20130101); A61B
5/15117 (20130101); A61B 5/15125 (20130101); A61B
5/15142 (20130101); A61B 5/15194 (20130101) |
Current International
Class: |
A61B
5/15 (20060101); A61B 017/14 () |
Field of
Search: |
;606/182,181,183-185
;600/573,538,578,576 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
WO 9637148 |
|
Nov 1996 |
|
WO |
|
WO 98/24366 |
|
Jun 1998 |
|
WO |
|
Other References
Softclix.RTM., "Lancet Device from the Makers of Accu-Chek.RTM.
Systems", (Product), PP. (3 pages), Becton Dickinson & Co.,
Franklin Lakes, New Jersey. .
One Touch.RTM. Profile.TM. "Diabetes Tracking System", Owner's
Booklet, (Product), PP.31-33, LifeScan Inc. .
Glucometer Elite.RTM., "Diabetes Care System", User's Guide,
(Product), PP. (3 pages), Miles Inc. Elkhart, IN..
|
Primary Examiner: Buiz; Michael
Assistant Examiner: Ngo; Lien
Claims
What is claimed is:
1. An apparatus for sampling blood from body tissue,
comprising:
(a) a lancet for lancing the body tissue to result in a wound for
bleeding;
(b) a housing operatively connected to the lancet and shielding the
lancet before lancing, the housing having an internal channel and a
head for contacting the body tissue in an air-tight manner against
suction forces, the housing having a piston which has sliding
motion along the housing when implementing suction at the head in
the reduction of air pressure at the body tissue prior to lancing
the body tissue to create a wound; and
(c) a driver for driving the lancet toward the body tissue for
lancing while the body tissue is under suction.
2. The apparatus according to claim 1 wherein the piston has a
channel along its length, the housing has a rear portion remote
from the lancet and wherein air passes through the channel of the
piston from the head to about the rear portion as the air pressure
at the head is being reduced, wherein the piston has a surface in
slidable contact with the housing in an air-tight manner.
3. The apparatus according to claim 1 wherein the piston is
slidably housed in the channel for air-tight sliding movement in
the channel against the housing in a direction away from the head
to reduce air pressure at the head.
4. The apparatus according to claim 1 wherein the head has a
depression and a pore connected together, the depression being more
towards the front of the head than the pore, both the depression
and the pore being at the front portion of the channel.
5. The apparatus according to claim 4 wherein the head has a ridge
encircling the depression for sealing against the body tissue.
6. The apparatus according to claim 5 wherein the lancet will
extend to protrude forward through the pore in the head when driven
for lancing, the protrusion of the lancet being not more forward
than the ridge to reduce the risk of inadvertent injury to a
user.
7. The apparatus according to claim 5 wherein the lancet protrudes
forward through the pore into the depression when driven to lance,
and wherein the head is adjustably secured in the housing to adjust
the protrusion into the depression.
8. The apparatus according to claim 3 wherein the driver includes a
spring which is compressed when the piston is moved to reduce air
pressure in the channel, the spring can be decompressed thereafter
to urge the lancet toward the body tissue.
9. The apparatus according to claim 8 wherein the housing further
comprises a catch for operatively holding the piston to maintain
the spring in a compressed state, wherein releasing the piston from
the catch will permit the decompression of the spring to drive the
lancet forward.
10. The apparatus according to claim 3 wherein the driver further
includes a means for moving the piston backward to reduce air
pressure in the channel before the piston is driven forward for
lancing.
11. The apparatus according to claim 2 wherein the piston carries
the lancet and has an open bore internally extending longitudinally
from proximate to the head to proximate to the rear portion
allowing air to pass through to a suction source at the rear
portion to reduce pressure in the channel at the head, thereby
sliding the piston forward by suction.
12. The apparatus according to claim 11 further comprising a
resilient support for allowing the piston to be pulled forward by a
reduction in air pressure at the head and retracting the piston
when the reduction in air pressure is removed.
13. A method for sampling blood from a body tissue, comprising the
steps of:
(a) providing a lancing device which has a lancet for lancing and
has a head with an opening for receiving blood from sampling and
further having a housing with a channel in the lancing device
extending longitudinally therein, the housing having a slidable
piston therein, the piston carrying the lancet;
(b) applying the head with the opening against the body tissue and
reducing air pressure in the channel at the head and on the body
tissue to a pressure less than the ambient pressure while slidably
moving the piston along the housing away from the head; and
(c) after step (b), puncturing the body tissue with the lancet.
14. The method according to claim 13 further comprising sliding the
piston in the channel away from the head to generate a reduced
pressure at the head when the head is applied against the body
tissue, the piston carrying the lancet for lancing.
15. The method according to claim 13 further comprising applying a
head having a ridge encircling a depression to seal the ridge
against the body tissue against air leakage before reducing air
pressure in the channel.
16. The method according to claim 15 further comprising extending
the lancet to protrude forward through the opening into the
depression for lancing and limiting the protrusion of the lancet to
no more forward than the ridge to reduce the risk of inadvertent
injury to a user.
17. The method according to claim 13 further comprising extending a
lancet forward through the opening into the depression for lancing
and adjusting the limit of extension of the lancet before extending
the lancet.
18. The method according to claim 13 wherein the channel includes a
head channel connected to a body channel and the method further
comprises moving the piston backward in the body channel to reduce
the air pressure in the head channel and compressing a spring at
the same time, the spring can be later decompressed to urge the
lancet toward the body tissue.
19. The method according to claim 13 further comprising moving the
piston backward and retaining it against the driving force of a
spring to result in reduced air pressure in the channel at the
head, and thereafter releasing the piston to allow the piston to be
driven forward by the spring for lancing.
20. A method for sampling blood from a body tissue, comprising the
steps of:
(a) providing a lancing device which has a lancet for lancing and
has a head with an opening for receiving blood from sampling and
further having a housing with a channel in the lancing device
extending longitudinally therein, the housing having a piston
disposed in the channel;
(b) applying the head with the opening against the body tissue and
reducing air pressure in the channel at the head and on the body
tissue to a pressure less than the ambient pressure, wherein the
step of reducing air pressure in the channel at the head and on the
body tissue comprises the substep of sucking air through a passage
extending longitudinally through the piston from the head to a
suction source proximate to a portion of the lancing device remote
from the head to effect a reduced pressure in the channel at the
head, the piston being slidable in the lancet device and carrying
the lancet such that the reduced pressure at the head causes the
piston to slide towards the body tissue for lancing; and
(c) after step (b), puncturing the body tissue with the lancet.
21. A method for inserting a lancet through the body tissue of a
patient, comprising the steps of:
(a) providing a lancing device having a housing and a lancet
carried by a slidable piston therein, the housing having a head and
a channel extending longitudinally in the housing and leading to an
opening in the head, the head for the lancet to extend therein for
lancing, the opening having a ridge encircling a depression for
receiving blood;
(b) applying the housing with the ridge against the body tissue,
such that the body tissue reaches into the depression;
(c) reducing the air pressure on the body tissue to a pressure less
than the ambient pressure by one of mechanically drawing air and
sliding the piston from the head to a rear portion of the housing
through the channel, wherein the air pressure on the body tissue is
being reduced while the piston is sliding along the housing;
(d) after the step (c) of reducing the air pressure on the body
tissue, puncturing the body tissue with the lancet by extending the
lancet in the channel forward in the opening to not pass the end of
the ridge; and
(e) receiving blood into the depression from the body tissue.
22. An apparatus for sampling blood from body tissue,
comprising:
(a) a lancet for lancing the body tissue to result in a wound for
bleeding;
(b) a housing operatively connected to the lancet and shielding the
lancet before and during lancing, the housing having an internal
channel and a head for contacting the body tissue in an air-tight
manner against suction forces, the housing having a piston which
can be slid in the housing in a direction away from the head to
implement suction at the head on the body tissue in the reduction
of air pressure at the body tissue prior to lancing the body tissue
to create a wound; and
(c) a driver for driving the piston to push the lancet toward the
body tissue for lancing while the body tissue is under suction, the
lancet not extending beyond the head during lancing.
23. An apparatus for sampling blood from body tissue,
comprising:
(a) a lancet for lancing the body tissue to result in a wound for
bleeding;
(b) a housing operatively connected to the lancet and shielding the
lancet before lancing, the housing having an internal channel and a
head for contacting the body tissue in an air-tight manner against
suction forces, the housing having a piston which has sliding
motion along the housing when implementing suction at the head in
the reduction of air pressure at the body tissue prior to lancing
the body tissue to create a wound, the piston being in rigid
relation to the lancet and has a channel extending longitudinally
from proximate to the head to proximate to the rear portion
allowing air to pass from the head through the piston to a suction
source at the rear portion to reduce pressure in the channel at the
head, thereby sliding the piston towards the head by suction from
the suction source; and
(c) a suction source for moving the lancet toward the body tissue
for lancing while the body tissue is under suction.
24. The apparatus according to claim 1, wherein the piston slides
along the housing while reduces air pressure on the body tissue by
one of expanding air space of air above the body tissue and
allowing air to pass through the piston to a suction source.
Description
FIELD OF THE INVENTION
The present invention is related to techniques for lancing skin
tissue with a lancet and drawing blood from it and more
particularly to apparatuses and methods for lancing skin tissue to
obtain an adequate sample with less pain.
BACKGROUND
The analysis and quantification of blood components is an important
diagnostic tool for better understanding the physical condition of
a patient. Since adequate noninvasive blood analysis technology is
not currently available, blood samples still need to be obtained
and analyzed by invasive methods from a great number of patients
every day. A well known example of such needs is self monitoring of
glucose levels by a diabetic individual, often performed in the
home of the individual. To obtain a blood sample it is necessary to
puncture the skin with a sharp object such as a lancet at a region
well supplied with blood vessels, for example, the fingertip. For
lancing, a lancet launcher is first loaded with a lancet and cocked
by pulling or rotating the cap on the launcher. The tip of the
launcher is then pressed against the skin and a button is pressed
to launch the lancet to strike the skin.
Currently available lancet launchers are typically pen-shaped
devices. The lancet is held in a cylindrical piston which is
propelled by a spring mechanism. On cocking, the spring serves to
store the energy required to propel the piston forward at the skin.
The propulsion of the lancet causes the lancet to impact against
and puncture the skin, causing a wound large enough for sampling
blood.
Such blood sampling is often painful and inconvenient. As a result,
many patients tend to not sample blood as frequently as suggested
by the health professionals to monitor the physiological functions
adequately. Moreover, for fear of pain in blood sampling, many
patients fail to use the lancet launchers properly. Such improper
use results in inadequate blood volume being collected and requires
repeating the lancing procedure, causing more pain and multiple
wounds.
What is needed is a lancet launcher for sampling blood that can be
used for sampling blood efficiently, so as to minimize pain to
encourage a patient to follow a routine for sampling blood as
directed by health professionals.
SUMMARY
In the present invention, the sampling of blood from body tissue is
facilitated by applying a negative pressure to the body tissue
before and while a lancet is launched to inflict a bleeding wound
in the body tissue. This negative pressure is mechanically
transmitted internally through substantially the body of the lancet
device. In this way, there is no cumbersome suction source attached
to the front part of the lancet device to hinder convenient
application of the lancet device to the body tissue.
In one aspect, the present invention provides an apparatus having a
lancet for sampling blood from body tissue. An embodiment of this
apparatus includes a lancet, a housing, and a driver that drives
the lancet for lancing. The lancing of the body tissue by the
lancet results in a wound for bleeding. The housing is operatively
connected to the lancet and shields it before lancing. The housing
has a head for contacting the body tissue in an air-tight manner
against vacuuming (i.e., suction) forces and having a channel in
which the air pressure can be reduced before the lancet is driven
to lance the body tissue. As an example, a piston can be included
in the channel for air-tight sliding movement against the channel
wall along the housing. Mechanical energy is transmitted via the
piston from near the rear of the lancet device to near the head to
result in reduced air pressure. In one embodiment, a rearward
movement of piston in the channel can cause the air pressure in the
channel near the head to be reduced before lancing. In another
embodiment, withdrawing air through a bore in the piston from the
front to the back of the piston while the front of the channel is
sealed by the body tissue allows the piston to slide forward to
drive the lancet toward the body tissue as the air pressure is
reduced at where the lancet device contacts the body tissue.
Currently, finger-prick devices do not provide enough blood for
certain tests that require larger volumes. Often large and multiple
wounds are required. For example, some patients, such as infants,
have veins that are difficult to locate for sampling through an
intravenous needle. In these patients the device of the present
invention can provide larger volumes for a smaller puncture wound.
Also, using the present apparatus, by reducing the environmental
pressure on the body tissue to increase its blood perfusion, the
depth of penetration by the lancet into the body tissue can be
reduced to provide an adequate blood sample. With a smaller
penetration depth, the trauma and pain of overpenetration is
avoided. Such reduction of discomfort and tissue damage can
significantly improve the willingness of patients to comply with,
for example, a blood sampling routine. The compact designs of the
present lancet devices allow the lancet devices to be conveniently
maneuvered without clustering around the lancing location on the
body tissue. This is significant for the precise positioning of the
lancet device on a desired location on the skin and one-handed
operation by a patient who may have lost substantial dexterity due
to a chronic illness.
BRIEF DESCRIPTION OF THE DRAWINGS
The following figures are included to better illustrate the
embodiments of the apparatus and technique of the present
invention. In these figures, like numerals represent like features
in the several views.
FIG. 1 shows in sectional view an embodiment of an apparatus of the
present invention.
FIG. 2 show an exploded sectional view in portion of the embodiment
of the apparatus of FIG. 1.
FIG. 3 shows the penetration into a body tissue by a lancet of an
embodiment of a lancing apparatus of the present invention.
FIG. 4A shows a sectional view in portion of the front part of a
lancing apparatus of the present invention.
FIG. 4B shows sectional view in portion of the front part of yet
another lancing apparatus of the present invention.
FIG. 5 shows an embodiment of an electrical driving mechanism
associated with a lancing apparatus for effecting a reduced
pressure on the body tissue.
FIG. 6 is a schematic representation that shows an embodiment of an
apparatus including an external suction source associated with the
lancet launcher.
FIG. 7 shows a schematic sectional view of an embodiment with a
piston having a bore for transmitting suction.
FIG. 8 shows a schematic sectional view of the embodiment of FIG. 7
where the lancet is driven forward.
DETAILED DESCRIPTION OF THE INVENTION
In one aspect, the present invention provides a technique for
obtaining an adequate amount of blood by puncturing body tissue
while applying a negative pressure to a body tissue to cause
bleeding in the body tissue. A bleeding wound can be created by
using a lancet. As used herein, a "lancet" is a shaft of any shape
having a sharp point or edge for cutting, puncturing, or incising
tissue, e.g., by including a blade, pin, needle, or the like.
FIG. 1 shows a sectional view of an embodiment of an apparatus for
sampling blood from a body tissue (e.g., skin) according to the
present invention. FIG. 2 shows an exploded sectional view in
portion of the embodiment of FIG. 1. For the sake of clarity of
depiction, the lower part of the body 104 (as viewed by the viewer
of the figure) is not shown in FIG. 2. In FIG. 1, the apparatus
(i.e., lancet launcher) 100 includes a body 104 and a head (or end
cap) 106. The head 106 is connected by screw threads 108 to the
front part 110 of the body 104 such that by turning the head 106
relative to the body 104, the head 106 can be moved more towards
the front or towards the back of the body 104. As used herein, the
terms "front," "forward," and "distal" refer to a position or
direction that is towards the end where the lancet is. Therefore,
these terms ("front, forward, distal," etc.) refer to a position
that is near the body tissue to be punctured when the lancet device
is applied to lance the body tissue. The terms "back," "rear,"
"backward," and "proximal" refer to a position or direction that is
away from the body tissue to be punctured. The screw threads 108
that connect the head 106 to the body 104 are adequately tight such
that air cannot leak through in the normal operation of the
device.
As seen in FIG. 1 and FIG. 2, the body 104 has a shell 109
encircling a channel (or lumen) 112 which extends backward from the
body's front part 110. A piston 114 can slide against the wall of
the channel 112 in an air-tight manner (i.e., there is no
substantial leak of air between the cylindrical surface of the
piston and the wall of the channel 112 in the shell 109).
Preferably the interface between the piston 114 and the channel
inside wall (or Luminal wall) 116 is such that there is little
friction hindering the sliding motion of the piston in the channel
112. To this end, the piston 114 and the channel inside wall 116
can be made or coated with a low friction material, such as
polytetrafluoroethylene. Optionally the interface between the
piston 114 and the channel inside wall 116 can be lubricated and
sealed against air leak by a liquid lubricant. Low friction
materials and lubricants are known in the art and a person skilled
in the art will be able to select such materials and lubricants
based on the present disclosure.
The distal portion of the piston 114 has a cavity 120 in which a
lancet block 122 is snugly secured. The lancet block 122 has a
lancet 124 at its distal end. When the piston 114 slides distally
forward, the piston 114 pushes the lancet block 122, and therefore
the lancet 124, forward to lance the body tissue.
The body 104 of the apparatus, further has a hollow cylinder 126
extending backward and encircling a stem 128 which is rigidly,
preferably integrally, connected to the piston 114. The stem 128
has a shaft 130 extending backward and through a back flange 132 to
connect to a sleeve cap 134 which has a cylindrical sleeve 136
encircling the shaft 130 and the back portion of the cylinder 126.
An actuating spring 140 is positioned between the stem 128 and the
back flange 132 such that when the piston is moved backward it
causes the stem 128 to compress the actuating spring 140 on the
back flange 132. The stem 128 has a cantilever 142 extending
distally and is pushed away from the stem 128 towards the channel
wall 116 by a spring 144 situated between the cantilever 142 and
the stem 128. The mid-portion 146 of the shell 109 has a well 148A.
When the piston 114 is moved (or pulled) backward adequately, a
finger catch 150 of the cantilever 142 is pushed into the well
148A. When the backwardly pulling force is terminated, the
compressed actuating spring 140 urges the stem 128 forward and the
finger catch 150 catches on the wall 148B of the well 148A and is
retained.
A triggering button 152 is situated in the well 148A above the
finger catch 150. Normally the triggering button 152 is urged away
from the axis of the channel 112 by a button spring 154. When the
triggering button 152 is pushed towards the axis of the channel
112, it dislodges the finger catch 150 from the wall 148B of the
well 148A. As a result, the actuating spring 140 drives the stem
128, and therefore the lancet 124, forward towards the body tissue
for lancing.
The head 106 also has a channel 156 which is connected to the
channel 112 of the body 104 in an air-tight fashion. The head 106
further has a distal ring-shaped ridge 158 encircling a depression
160, which joins by a pore 162 to the proximal portion of the head
channel 156. The distal end of the ridge 158 when pressed against
the body tissue seals to prevent air leakage such that when the
piston 114 is pulled backward the void volume in the head channel
156 is increased, thereby reducing the air pressure therein to a
pressure less than that of the ambient pressure, i.e., the air
pressure external to the head 106. Due to the reduced pressure,
blood perfusion in the body tissue against the depression 160 is
increased.
While the body tissue facing the depression 160 is still under
negative pressure (i.e., under a pressure less than that of the
ambient pressure), the trigger button 152 is pressed to release the
finger catch 150 from the well 148A, thereby driving the lancet
forward. Due to its flexibility, when the body tissue 164 is
pressed against the ridge 158 the body tissue will extend into the
depression 160. Preferably, the depression is made deep enough that
it is not necessary for the lancet to extend all the way past the
distal end of the ridge 158 for lancing to result in a puncture
wound deep enough for blood sampling (see FIG. 3). In this way, the
ring-shaped ridge 158 will help to prevent inadvertent injuries to
the patient (or user) by an exposed lancet.
Preferably, the head 106 is snugly but detachably connected to the
shell 109. As shown in FIG. 4A, the head 106 can be connected by
screw-threads with the shell 109 in an air-tight manner. By
adjusting the position of the head 106 on the shell 109, the
distance that the lancet 124 when launched can extend past the pore
162 can be adjusted. In an apparatus shown in FIG. 4B, the head 106
is held in an air-tight manner by friction on an intermediate
sleeve 165, which is threadedly (i.e., by screw-threads) connected
to the shell 109. After use, the head 106 can be conveniently
detached by pulling from the sleeve 165.
Driving Mechanisms
A wide variety of energy sources can be used for creating the
negative pressure and for driving the lancet. The mechanical
piston, catch and spring mechanism described above and shown in
FIG. 1 is suitable for manual operation by an individual. As an
alternative, shown in FIG. 5, the piston 114 (as that of in FIG. 1)
can be pulled backward by an electric motor 166 by means of a cord
168 on a spool 170 to cock the stem 128 against the spring 140 (as
those of FIG. 1) and create the negative pressure. A trigger 172
can be used to initiate the backward pulling of piston 114 by the
motor 166. The motor 166 can either be activated by alternate
current or by direct current, such as using batteries. Further,
electronics can be included in the lancing apparatus such that once
the trigger is actuated, (e.g., after the piston 114 has been
pulled back to result in reduced pressure, and an adequate distance
has been reached) the piston 114 will be suddenly released and
allow the forward driving force (e.g. from the driving spring 140)
to launch the lancet forward for lancing. Such electronics can be
enclosed, for example, are the motor region or in the housing of
the lancing apparatus. Electronics that can perform these functions
in within the skill of one skilled in the art.
Furthermore, separate mechanisms can be used for creating the
negative pressure and independently for driving the lancet. For
example, as illustrated in FIG. 6, a vacuum (or suction) source 174
can be connected to the channel (similar to channel 156 of FIG. 1)
of the lancing apparatus 176. With the skin tissue 164 under
negative pressure, the lancet can be driven, e.g., by the spring
mechanism (similar to spring 140 of FIG. 1) toward to the skin
tissue for lancing. Additionally, the lancet can further be driven
mechanically, electrically, pneumatically, or hydraulically. Such
mechanisms for driving a shaft forward are known in the art and can
be adopted to apply in the present lancing technique by one skilled
in the art.
Using Vacuum (Suction) for Increasing Perfusion and Driving the
Lancet
In another aspect, the present invention provides a technique for
using vacuum (i.e., suction) to increase perfusion of a body tissue
and drive the lancet to puncture (or incise, cut, etc.) the body
tissue simultaneously. FIG. 7 shows an embodiment that has this
advantage.
In FIG. 7, a blood sampling apparatus 170 has a body 172 attached
to a driver head 174. The body 172 includes a tubular shell 176 in
which a piston 178 can freely slide. A flexible diaphragm 179
separates the body 172 and the driver head 174 in an air-tight
fashion. A vacuuming port (i.e., suction port) 180 provides access
to a suction source (or vacuum source, arrow AR indicates the
direction of gas flow to the suction source V). A bore (or passage)
181 in the piston 178 allows air to pass therethrough and the air
pressure on the two sides of the piston 178 to equilibrate. The
piston 178 is rigidly supported from the diaphragm 179 by rod 182
such that movement of the diaphragm 179 will cause the piston 178
to move. The void area inside the tubular shell 176 between the
piston 178 and the diaphragm 179 forms a chamber 184. When a body
tissue (such as the flesh of a finger) 186 seals the end 188 of the
tubular shell 176 distal from the diaphragm 179, a chamber 190,
bordered by the body tissue 186, a distal portion of the shell 176,
and the piston 178, results. The piston 178 holds a lancet 194 at
an end (the distal end) opposite to the driver head 174.
The driver head 174 has an air-tight cap 196, which has an openable
vent 198 to allow air pressure to equilibrate between the
atmosphere external to apparatus 170 and a chamber 202 inside the
driver head 174. A resilient support 204 (such as compressible
object, e.g., a resilient bead or a spring) extends from the
diaphragm 179 to the end of the cap 196 on the side of the driver
head 174 opposite to the diaphragm 179. The compressible bead can
be made with a resilient material such as a polymeric substance.
Further, the compressible bead can be solid or a bladder filled
with a fluid, such as a gas or a liquid.
In operation, as shown in FIG. 8, a suction pulse (can be referred
to as a "vacuum pulse") of a predetermined duration and amplitude
is applied to the suction port 180. The negative pressure is
transmitted to the chamber 184, and through the bore 181 to the
chamber 190. The negative pressure in the chamber 184 causes the
diaphragm 179 to flex forward (i.e., towards the lancet 194),
thereby extending the resilient support 204. This forward extension
of the diaphragm 179 causes the piston 178 to move a finite
distance. The negative pressure communicated through the bore 181
to the chamber 190 causes the tissue to be sucked against the
forward end 188 of the tubular shell 176 and increases the blood
flow to that tissue. The simultaneous movement of the advancing
lancet and the suction on the tissue against the tubular shell 176
drives the needle 194 to puncture the tissue of the finger 186,
thereby causing bleeding from the puncture wound. Thus, blood 210
is emitted from the lancing wound and is sampled from the finger
tissue by the application of suction. The suction source provides
the driving force for driving the lancet 194, as well as providing
the reduced environmental pressure on the tissue to increase blood
flow and bleeding. The removal of the suction restores the piston
178 to its original position of FIG. 7.
Although preferred embodiments of the present invention have been
described and illustrated in detail, it is to be understood that a
person skilled in the art can make modifications within the scope
of the invention.
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